A press filter is well-known to find a wide range of applications in chemistry, petroleum, mining, foods and pharmaceutical industries for separation of solids from liquids. Generally, the press filter comprises a plurality of filter plates arranged in parallel from one another for the separation of solids from liquids, a frame on which the plurality of filter plates are supported, a pressure mechanism for pressing the plurality of filter plates together during the filtration cycle, and a cake discharge mechanism. Each of the filter plates comprises a supporting plate which is recessed on both sides and filter elements such as filter cloth covered on both sides of the supporting plate. Once pressed together, the plurality of filter plates form a series of chambers.
Generally, the supporting plates have a central through hole that passes through the entire length of the press filter so that all the chambers of the filter plates are connected together, and the slurry or the suspension is fed through the central through hole into the chambers. The filtrates permeates the filter cloth and flow downward along the wall of the supporting plate.
Four corner ports are provided on each supporting plate to connect all the plates, wherein the top two corner ports are to introduce washing liquid or compressed air, and the bottom two corner ports are to collect the filtrates that permeate the filter cloth towards outlets and then are drained away. The cakes are formed on the face of the filter cloth and fill the chambers. The cakes are compressed and dewatered during the filtration cycle and the cake thickness increases over time. Once the optimum combination of chamber filling and cake dryness is achieved, the filtration is stopped, the pressure is relieved and the cakes are discharged by the cake discharge mechanism. A new filtration cycle starts.
Presently, the basic design to install the filter cloth on both sides of the supporting plate is to sew the filter cloth into a sack into which the supporting plate is inserted, or to stretch out two pieces of filter cloth over two sides of the supporting plate. The filter cloth has a hole positioned to correspond to the central through hole of the supporting plate, and the two pieces of the filter cloth are pressed against each other by a connecting means which is either sewn or bonded to the edges of the cloth holes and then is mounted on the central through hole of the supporting plate. To install the filter cloth on the supporting plate, it is necessary to align the central through hole of the supporting plate and the cloth hole, and the connecting means is connected with the filter cloth and with the central through hole of the supporting plate in a leak-proof manner. If the central through hole and the cloth hole are not aligned, the operation of the press filter would be less effective, and the leakage may occur and result in low filtration rate. Further, it is often that damage to the filter cloth may take place when the connecting means connects the filter cloth and the filter cloth is mounted on the central through hole of the supporting plate, which makes the cloth unusable. As can be seen, the current methods of installing the filter cloth on the supporting plate are very labor intensive with a high risk of leakage and damage to the cloth.
Various efforts have been made in order to solve the problems associated with filter cloth installation and filter cloth leakage. For example, US patent application no. 2010/0200518A1 provides a filter element for a press filter, comprising first and second filtering means, first and second connecting means and a securing ring. Each of the first and second connecting means comprises a flange portion and a tubular portion, wherein the flange portion of the first connecting means is fixedly attached to the first filtering means and the flange portion of the second connecting means is fixedly attached to the second filtering means, and wherein the tubular portion of the first connecting means is insertable into the tubular portion of the second connecting means. The securing ring is insertable into the tubular portion of the first connecting means and is adapted to exert a radial force on the tubular portion of the first connecting means, pressing the tubular portion of the first connecting means against the tubular portion of the second connecting means, thereby to realize the purpose of robustness and leak resistance. It is to be noted that the securing ring is needed for pressing the first filtering means against the second filtering means, which results in complicated replacement of the filter cloths. Moreover, when the securing ring is damaged or when the securing ring is installed in a manner that the first and second connecting means cannot be locked in place by the securing ring, the leakage phenomenon would take place.
Non-woven fabric is a cloth that is neither woven nor knitted. The non-woven fabric exhibits good filterability, permeability and absorption, and therefore is suitable to be used as a filter medium.
The international application under PCT/CN2011/071371 filed by the applicant on 28 Feb. 2011 discloses a e non-woven fabric, a method for producing the fabric, and a filter formed with the fabric. The non-woven fabric is made of at least one low-melting-point short fiber and at least one high-melting-point short fiber, and characterized in that the low-melting-point fiber is a solidifiable material, particularly is capable of solidifying after it is heated to melt, whereby the obtained felt fabric has the ability of self-sustaining and shape maintenance. The felt fabric disclosed in this patent application can also be molded into various shapes according to the actual needs and has a characteristic of being-persistently retaining in those shapes after it is molded. Therefore, the fabric exhibits excellent hardness and stiffness, remarkable moldability, and high compressive strength, in addition to the conventional properties of good filterability, permeability and absorption.
Another international application under PCT/CN2011/084323 filed by the applicant on 21 Dec. 2011 discloses a novel non-woven fabric, a method for producing the fabric, and a filter formed with the fabric. This non-woven fabric is made of one short fiber of the same type, or two or more types of short fiber which have a substantially same melting point, and characterized in that about 30% to 80% of the short fiber is heated to melt and then solidifies so as to form a single melting point non-woven fabric. It was tested that the single melting point non-woven fabric obtained as such is also stiff to have the ability of self-sustaining and shape maintenance, and exhibits excellent hardness and stiffness, remarkable moldability, and high compressive strength, in addition to the conventional properties of good filterability, permeability and absorption.
In light of the unique characteristics of the non-woven fabric discussed above, especially self-sustaining and shape maintenance, remarkable moldability and excellent filterability, the non-woven fabric may be molded into various elements used in the different types of filters. The molded elements not only make it possible that the labor intensity of installing and assembling the elements is greatly reduced, but also that the connection of the various molded elements from one another is more intimate and robust.